Effect of Class F Rotor in Class B Stator Generator?

[AJ2002]

What is the effect of having a class F rotor installed in a class b generator stator? There is two generators both 50MW at 13.8KV 60Hz. One has a bad stator and one has a bad field rotor. Can they be combined to make one good generator? What would the final insulation level be?

If someone has a good reference site on the generator design and the insulation classes and temperature rise for me it would be greatly appreciated. Thank You.

 

[motorsdirect]

With Class B being the insulation class...the insulation class of the generator will drop to class B.
And otherwise all should be fine as long as the windings details and dimentions are the same.
hope this helps
Jeff

http://www.motors-direct.co.uk

 

[ScottyUK]

Of course the rotor could run at a Class F rise provided that the stator does not see a rise exceeding Class B. That could potentially happen with a load with a heavy lagging power factor, requiring a high field current to deliver the reactive power.

Most stators of that size will have a fair number of stator RTDs, and the stator temperature will trigger either an unload or trip when the temperature exceeds a threshold. If you treat the combined unit as a Class B machine you shouldn't have any problems, provided the rotors are identical other than the insulation class.

Is the stator definitely Class B? It is quite common to design a machine to achieve a Class B rise, but insulate it to Class F. Worth checking out.


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[electricpete]

I agree with the all the above comments. If the 2 machines are identical except for the insulation, then you could definitely combine the components and run with loading limit determined to avoid exceeding temperature limits - most likely the stator class B temperature would be limiting except in unusual case mentioned above.

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[aolalde]

The following link will give you information on the insulation class.

http://www.joliet-equipment.com/temperature_classifications.htm

As stated above most important are the winding parameters to be compatible rather than the class F insulation, which will be an advantage if the stator is rated and limited to operate under insulation class B.

 

[powerjunx]

AJ2002,

50MW generator is a big thing, stator class B insulation is somewhat intriguing! maybe it's higher than B. Try to check it out!

If it really identical and only it differs on their insulation class, you may have no problem. The heating effect on stator winding will be conveyed and taking care by the temperature monitoring device that senses the stator winding temperature.

Moreover, rotor and stator insulation is limited on generator's capability curve that is, low power factor (lagging) affects rotor heating while leading PF will affects the stator.